Beam Failure Reporting via MAC CE for Fast Recovery
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Solution Overview
Problem
In 5G NR wireless communication systems, user equipment (UE) experiences prolonged beam recovery times due to the need for contention-based random-access procedures when signal quality is poor, often resulting in inefficient use of limited preambles and time-frequency resources.
Innovation Solution
The UE initiates a beam recovery procedure by transmitting a Media Access Control Protocol Data Unit with a MAC Control Element indicating Synchronization Signal Blocks, allowing the base station to dynamically select a downlink transmit beam with lighter traffic load, thereby reducing the time required for beam recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If contention-based random-access procedure is used for beam recovery, then the procedure can be performed without dedicated resources, but the beam recovery time is prolonged
Solution Approach 1:
The network pre-configures dedicated preambles and time-frequency resources for beam failure recovery before the actual beam failure occurs. When beam failure is detected, the UE can immediately use these pre-configured resources to initiate recovery, avoiding the time-consuming contention-based random access procedure and enabling faster beam recovery
2Loss of time
If dedicated preambles and time-frequency resources are allocated for beam recovery, then beam recovery time is reduced, but the limited resources are consumed faster
Solution Approach 1:
The system dynamically adjusts parameters such as the number of dedicated preambles, their distribution across different beams, and the periodicity of resource allocation based on network conditions, traffic load, and beam failure statistics. This optimization ensures efficient resource utilization while maintaining fast beam recovery capability
3Device complexity
If multiple UEs use the same dedicated preambles and time-frequency resources for beam recovery, then resource allocation is simplified, but resource conflicts and interference increase
Solution Approach 1:
The system segments dedicated preambles and time-frequency resources across multiple beams and spatial directions. Each beam or spatial region is assigned specific preambles and resources, reducing the probability of conflicts when multiple UEs simultaneously initiate beam recovery. This segmentation maintains relatively simple resource allocation while significantly reducing resource conflicts and interference
Data Source
AI summary
This document describes reporting beam failure by a user equipment (110) to a base station (121) in a radio access network (140), in which the user equipment (110) receives a first uplink grant (502) and initiates a beam recovery procedure (504). Based on the beam recovery procedure determining that a beam has failed, the user equipment (110) transmits, using the first uplink grant, a first Media Access Control Protocol Data Unit including a first MAC Control Element that indicates a first Synchronization Signal Block and a second Synchronization Signal Block, the transmission being effective to cause the base station (121) to determine that, based on receiving the first Synchronization Signal Block, the beam failure was detected by the user equipment (110) on the first Synchronization Signal Block (506).